1. Field of the Invention
The present invention relates to polymers and methods of producing the same, the polymers having film-forming characteristics and the films produced therefrom having water-barrier properties at substantially neutral pH's and yet being substantially completely solubilizable at non-neutral pH's. More particularly, the invention relates to silane-crosslinked interpolymers of alkyl acrylates and, in a preferred embodiment, acrylic acid, and disposable products produced therefrom.
While the composition and products of the present invention are herein described primarily in connection with advantageous applications in the medical and sanitary product fields, it should be understood that the present invention is not limited thereto. In the light of the present disclosure, those skilled in the art will recognize a variety of applications in other fields wherein the moisture impermeability and film-forming characteristics of the alkaline-labile or acid-labile silane-crosslinked polymers of the present invention may be advantageously employed.
2. Description of the Prior Art
There has long been a need in the handling of waste products of the liquid or semi-liquid type, such as body exudates, to have a material which would contain the waste when excreted but which could then be readily disposed of later. In hospital use, for example, there are bedpans, urinals, emesis basins, bags for wound irrigation, bags for incision and drainage of abscesses, bags for urine collection, bags for ostomies, i.e., ileostomies, colostomies, etc., and other containers which are used daily for the collection of body exudates in a liquid or semi-liquid form. Similarly, in home use, body exudates are collected in bandages, pads, diapers and similar sanitary products. The problem of convenient, sanitary, esthetic and inexpensive disposal is ever present.
One prior art approach has been to utilize various plastic materials, such as polyethylene, to form water-impervious containers, barriers or liners for collection of the body exudates. The waste material and the plastic film can then be dropped into a toilet bowl and the liquid or semi-liquid waste flushed away. But the problem of disposal of the plastic film, which is not soluble, still exists. The film can not be flushed away without ultimately causing plumbing and sewage treating problems. Instead, it is retained and collected in containers, the contents of which are later incinerated or dumped into a trash disposal area. Quite aside from the esthetic problem and the attendant inconvenience and cost, the practice is undesirable from the standpoint of possible spread of contamination or disease.
Another prior art approach is described in U.S. Pat. No. 3,480,016, issued Nov. 25, 1969, and entitled "Sanitary Products". This patent discloses, for example, toilet-flushable sanitary products comprising biodegradable fibers bonded together by a resin. The resin is stable to body discharges which have pH's ranging from about 4.6 to about 8.4, but is solubilizable under selected acid or alkaline conditions substantially outside this range. The polymers employed, however, are unduly hydrophilic in nature and in practice do not form films having true moisture-barrier properties. Accordingly, while the polymers, as well as associated absorbent materials, can be disposed of along with the waste material by solubilizing the same, certain applications require the presence of a supplementary moisture barrier, thus rendering the product not truly disposable in its entirety and complicating the disposal problem, as already described. That is, the polymers described in U.S. Pat. No. 3,480,016 are not crosslinked in any manner and are not suitable for forming films with water barrier properties, but can only be used as binders for "sanitary products".
British Pat. No. 1,127,625 discloses generally the use of alkoxy-silyl-alkyl monomers as crosslinking agents for polymers such as acrylate polymers for pressure-sensitive adhesives. This patent, however, contains no suggestion either of producing films having water-barrier properties at neutral pH's that are also solubilizable in aqueous media at substantially non-neutral pH's, nor of the particular silane monomers and proportions thereof that I have found to be critical, in accordance with the present invention, for producing polymers from which such films can be manufactured.